List of Excipients in Branded Drug METOPIRONE

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Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
ESTEVE PHARMACEUTICALS SA	METOPIRONE	metyrapone	68118-455	4-ACETYLANISOLE
ESTEVE PHARMACEUTICALS SA	METOPIRONE	metyrapone	68118-455	ETHYL VANILLIN
ESTEVE PHARMACEUTICALS SA	METOPIRONE	metyrapone	68118-455	GELATIN
ESTEVE PHARMACEUTICALS SA	METOPIRONE	metyrapone	68118-455	GLYCERIN
ESTEVE PHARMACEUTICALS SA	METOPIRONE	metyrapone	68118-455	POLYETHYLENE GLYCOL 400
ESTEVE PHARMACEUTICALS SA	METOPIRONE	metyrapone	68118-455	POLYETHYLENE GLYCOL 4000
ESTEVE PHARMACEUTICALS SA	METOPIRONE	metyrapone	68118-455	PROPYLPARABEN SODIUM

Metopirone Excipient Strategy, Patent Position, and Commercial Opportunities

Last updated: October 30, 2026

Metopirone is the brand name for metyrapone, a steroidogenesis inhibitor used for diagnostic assessment of the hypothalamic-pituitary-adrenal axis and for medical management of hypercortisolism. Its commercial opportunity is concentrated in specialty endocrinology rather than mass-market chronic therapy. The active ingredient is an established small molecule with limited composition-of-matter protection. The strongest opportunities are therefore in formulation differentiation, supply reliability, regulatory lifecycle management, and geographic expansion.

The current dosage form is a 250 mg hard capsule. Public product information identifies conventional excipients, including lactose monohydrate, maize starch, talc, and magnesium stearate, with gelatin and coloring agents in the capsule shell.[1] This creates opportunities for lactose-free, modified-release, pediatric, hospital-use, and stability-optimized presentations.

What is Metopirone and how is it used?

Metopirone contains metyrapone, an inhibitor of 11-beta-hydroxylase, the enzyme that converts 11-deoxycortisol to cortisol. The resulting increase in 11-deoxycortisol is used diagnostically to assess pituitary-adrenal function. Metyrapone is also used to reduce cortisol production in patients with Cushing's syndrome when surgery is unavailable, unsuccessful, delayed, or insufficient.[1,2]

Attribute	Metopirone
Active ingredient	Metyrapone
Dosage form	Hard capsule
Common strength	250 mg
Primary mechanism	11-beta-hydroxylase inhibition
Main uses	Metyrapone test; hypercortisolism management
Therapeutic area	Endocrinology
Product type	Established small-molecule medicine
Biosimilar relevance	None
Principal commercial market	Specialty and hospital endocrinology

Metyrapone has a short pharmacologic duration compared with several chronic cortisol-lowering products. That property is useful for diagnostic testing and allows dose adjustment during acute cortisol control, but it can require multiple daily doses in treatment settings.[1]

What excipients are used in Metopirone capsules?

The conventional Metopirone formulation uses a standard immediate-release hard-capsule platform. The listed excipient system includes lactose monohydrate, maize starch, talc, and magnesium stearate. The capsule shell contains gelatin and permitted colorants.[1]

Formulation component	Likely function	Commercial implication
Lactose monohydrate	Diluent and bulking agent	Creates a lactose-free reformulation opportunity
Maize starch	Filler and disintegration aid	Can be replaced with directly compressible or low-moisture alternatives
Talc	Glidant and anti-adherent	Requires control of particle size and regulatory grade
Magnesium stearate	Lubricant	Excessive levels may affect dissolution
Gelatin shell	Capsule shell material	Vegetarian, halal, kosher, or low-moisture alternatives are possible
Titanium dioxide or iron oxides	Color identification	Can support product differentiation but may face jurisdiction-specific restrictions

The existing excipient profile is commercially functional but not highly differentiated. A competing product would need to demonstrate a practical benefit, such as improved tolerability, reduced moisture sensitivity, better capsule opening, simplified administration, or improved supply-chain performance.

Lactose-free formulation

A lactose-free formulation is the clearest excipient opportunity. Potential replacements include microcrystalline cellulose, mannitol, dibasic calcium phosphate, pregelatinized starch, or a combination of these materials. Selection must account for:

• Metyrapone content uniformity at the 250 mg dose;
• powder flow and capsule-filling performance;
• dissolution under immediate-release conditions;
• compatibility with moisture and oxygen;
• excipient-related impurities;
• capsule-shell brittleness;
• patient use in hospitals and endocrine clinics.

A lactose-free version could target patients with lactose intolerance, institutions using excipient-restricted formularies, and markets where lactose labeling creates prescribing or procurement friction. The commercial value is likely incremental rather than transformational because lactose intolerance does not automatically create a clinical contraindication to the existing product.

Vegetarian and specialty capsule shells

Replacing gelatin with hydroxypropyl methylcellulose or pullulan could expand use in vegetarian, halal, kosher, and selected institutional markets. The primary technical risks are shell moisture transfer, brittleness, oxygen permeability, fill compatibility, and dissolution equivalence.

A shell change may support a line extension but is unlikely to justify premium pricing without a documented market-access benefit. A gelatin-free capsule has greater value in countries or hospital systems with formal excipient restrictions.

Low-moisture formulation

Metyrapone products should be assessed for moisture sensitivity, solid-state changes, and capsule-shell interaction. A low-moisture formulation could use an anhydrous or low-water-activity filler system and high-barrier packaging. Options include:

• aluminum-aluminum blister packaging;
• high-density polyethylene bottles with desiccant;
• moisture-scavenging secondary packaging;
• low-water-activity fillers;
• nitrogen-flushed packaging where justified by stability data.

Packaging may provide a faster commercial improvement than a new excipient system. A stability-enhanced presentation could reduce wastage in hospital inventories and support distribution into hot or humid markets.

What formulations are protected by Metopirone patents?

Metopirone is an old small-molecule product, so composition-of-matter protection for metyrapone is not commercially relevant. The principal intellectual-property opportunities would involve later-developed formulations, manufacturing processes, crystal forms, packaging systems, or method-of-use claims.

IP category	Expected position	Commercial relevance
Metyrapone composition of matter	Expired or commercially unavailable	No meaningful entry barrier
Conventional capsule formulation	Weak unless supported by a later patent	Limited exclusivity
Lactose-free formulation	Potentially patentable if technically specific	Moderate lifecycle value
Modified-release formulation	Potentially patentable	High development and clinical risk
Pediatric liquid or multiparticulate dosage form	Potentially patentable	Niche but differentiated
Manufacturing process	Potentially protectable	May create supply advantage
Packaging and stability system	Usually limited patent strength	Useful as know-how or trade secret
Method of use	Potentially relevant for defined patient populations	Regulatory and enforcement value depends on jurisdiction

A reformulation patent must claim more than the substitution of one routine excipient for another. Patent strength improves when the formulation produces a measurable, non-obvious result, such as improved dissolution after accelerated storage, reduced degradation, enhanced content uniformity, or a clinically useful pharmacokinetic profile.

How strong is the Metopirone patent estate?

The patent estate is likely weak for the active ingredient and conventional immediate-release capsule. The stronger barriers are regulatory, manufacturing, supply, and market-access barriers.

A generic or alternative manufacturer would face several practical requirements:

1. Establish pharmaceutical equivalence to the reference product.
2. Demonstrate acceptable dissolution and content uniformity.
3. Reproduce or appropriately replace the excipient system.
4. Validate impurity controls for metyrapone and degradation products.
5. Secure a reliable active pharmaceutical ingredient supply.
6. Address small-market economics and limited manufacturing scale.

For the United States, Orange Book-listed patents and exclusivity would control an ANDA strategy if a currently listed reference product exists. For Europe, a generic or hybrid application would rely on the applicable national or centralized pathway, depending on the product's authorization basis and intended claims.[3,4]

No biosimilar pathway applies. Metyrapone is a synthetic small molecule, not a biologic.

When does Metopirone lose exclusivity?

The original active-ingredient exclusivity for metyrapone has long expired. Commercial exclusivity today is more likely to arise from:

• regulatory exclusivity linked to a new indication;
• orphan-drug designation in a qualifying jurisdiction;
• pediatric investigation incentives;
• a new dosage form;
• a clinically differentiated formulation;
• a patented manufacturing process;
• a device or combination product.

A conventional 250 mg capsule containing the same active ingredient would generally offer limited exclusivity potential. A new product would need a specific regulatory or patent hook to delay competition.

U.S. FDA status and Orange Book considerations

Metyrapone has an established regulatory history as a diagnostic and cortisol-lowering medicine. The commercial analysis must distinguish between:

• an FDA-approved reference product;
• a product marketed under an older approval;
• an unapproved or medically used product;
• an imported product;
• an ANDA-eligible reference standard.

If a U.S. reference product is not actively marketed or does not provide a straightforward ANDA pathway, a 505(b)(2) strategy may offer greater flexibility. A 505(b)(2) application could rely partly on published literature or an approved product while supporting a new formulation, strength, route, or indication.[3]

European regulatory position

In Europe, Metopirone has been marketed through national authorization systems. A new applicant could evaluate a generic, hybrid, or well-established-use strategy, depending on the target country, reference product, and proposed labeling. A new indication for treatment of endogenous Cushing's syndrome could require clinical support beyond a simple pharmaceutical-equivalence package.[1,4]

What generic entry risks exist for Metopirone?

Generic entry risk is technically moderate and commercially uneven.

Technical entry risk

The immediate-release capsule is not inherently difficult to manufacture. The main CMC issues are likely to be:

• drug-excipient compatibility;
• dissolution consistency;
• assay and content uniformity;
• control of related substances;
• capsule-shell stability;
• supply of high-quality metyrapone API;
• packaging performance under long-term storage.

A direct generic could likely avoid major formulation complexity if the reference product's composition and performance are well characterized.

Commercial entry risk

The market is specialized, and patient volumes are lower than those for common endocrine medicines. This reduces the incentive for multiple generic manufacturers but can increase the value of a reliable supplier. A shortage or discontinuation by the incumbent could create an opening for a second-source manufacturer.

The most attractive entry model is likely a focused specialty product with:

• dependable API supply;
• broad geographic registration;
• hospital procurement support;
• rapid availability for diagnostic testing;
• competitive but sustainable pricing;
• a differentiated excipient or packaging profile.

What commercial opportunities exist for Metopirone excipients?

1. Lactose-free immediate-release capsule

This is the lowest-risk lifecycle project. It could use microcrystalline cellulose, mannitol, or pregelatinized starch. The product would remain close to the established dosage form, reducing clinical and regulatory complexity.

2. Pediatric-friendly dosage form

Metyrapone is used in endocrine disorders that may affect children and adolescents. A multiparticulate capsule, oral powder, or oral suspension could improve dose flexibility. The main barriers are taste masking, suspension uniformity, preservative selection, dosing-device accuracy, and stability after reconstitution.

A pediatric formulation could support pediatric exclusivity or other regulatory incentives in some jurisdictions, but the commercial market would remain limited.

3. Modified-release metyrapone

A sustained-release formulation could reduce dosing frequency and limit peak-related adverse effects. The opportunity is technically attractive but clinically demanding. Metyrapone's short action is also part of its clinical utility, especially when clinicians need rapid dose adjustment. A modified-release product would therefore require evidence that prolonged exposure improves treatment without reducing controllability.

4. Hospital diagnostic kit

A diagnostic-use presentation could combine standardized capsules, administration instructions, timed sampling materials, and laboratory workflow support. The kit itself may not create substantial patent protection, but it could improve adoption and reduce errors in metyrapone testing.

5. High-barrier packaging

A packaging-led product could target countries with hot, humid climates or distribution systems with extended storage periods. Aluminum blistering and improved moisture control may offer a practical competitive advantage without changing the core formulation.

6. API and manufacturing partnerships

The most valuable opportunity may be supply-side rather than excipient-based. A manufacturer with qualified metyrapone API, validated impurity controls, and regulatory documentation could become a regional or global second source. Process know-how, analytical methods, and reliable batch release can be protected through trade secrets and regulatory execution even when patent protection is limited.

How does Metopirone compare with competing cortisol-lowering drugs?

Product	Active ingredient	Main commercial distinction	Formulation opportunity
Metopirone	Metyrapone	Rapid cortisol synthesis inhibition; diagnostic use	Lactose-free, pediatric, modified-release, packaging
Isturisa	Osilodrostat	Chronic cortisol control with newer regulatory positioning	Less direct generic comparison
Korlym	Mifepristone	Glucocorticoid receptor antagonism	Different mechanism and safety profile
Signifor	Pasireotide	Somatostatin-receptor-based therapy	Injectable and long-acting platform
Ketoconazole products	Ketoconazole	Established steroidogenesis inhibition	Broad generic competition and tolerability concerns

Metyrapone's strongest differentiation is its diagnostic role and rapid, titratable effect. Its weakest commercial attributes are the small patient population, possible need for repeated dosing, and limited intrinsic product differentiation.

What patent litigation and settlement issues affect Metopirone?

No major, widely recognized patent-litigation framework comparable to high-revenue branded medicines is associated with conventional metyrapone capsules. Paragraph IV risk would arise only if a current U.S. reference product had enforceable listed patents or if a branded reformulation introduced new patent claims.

A challenger should evaluate:

• Orange Book-listed patents;
• use codes for Cushing's syndrome or diagnostic testing;
• patent term adjustment;
• pediatric exclusivity;
• orphan exclusivity;
• pending applications on new formulations;
• any supply or distribution settlement restricting launch.

For an old small-molecule capsule, litigation exposure is more likely to center on regulatory interpretation, manufacturing quality, or supply continuity than on foundational patent claims.

Key Takeaways

• Metopirone contains metyrapone and is used for adrenal-axis testing and hypercortisolism management.
• The conventional capsule uses lactose monohydrate, maize starch, talc, magnesium stearate, gelatin, and colorants.
• The most practical excipient opportunity is a lactose-free, immediate-release capsule.
• Vegetarian capsule shells, pediatric dosage forms, high-barrier packaging, and diagnostic kits provide secondary opportunities.
• Composition-of-matter protection for metyrapone is not a meaningful commercial barrier.
• Generic entry risk is technically manageable but moderated by small-market economics and API supply requirements.
• No biosimilar risk applies.
• A 505(b)(2), hybrid, or well-established-use strategy may be more attractive than a conventional generic route in some jurisdictions.
• The strongest defensible assets are likely to be formulation data, process know-how, stability performance, regulatory exclusivity, and reliable supply.

FAQs

Is Metopirone lactose-free?

No. Public product information identifies lactose monohydrate among the excipients in the conventional Metopirone capsule.[1]

Can metyrapone be formulated as an oral liquid?

Potentially, but an oral liquid would require development work on solubility, taste masking, dose uniformity, preservative effectiveness, and in-use stability. A suspension or multiparticulate system may be more practical than a true solution.

Is there a commercial opportunity for a generic Metopirone capsule?

Yes. The opportunity depends on reference-product availability, jurisdictional regulatory status, API sourcing, and the ability to achieve profitable scale in a specialty endocrine market.

Could a lactose-free Metopirone formulation receive patent protection?

Possibly, but routine excipient substitution alone is unlikely to provide strong protection. Patentability would improve if the formulation produced unexpected stability, dissolution, bioavailability, or manufacturing results.

Does Metopirone compete directly with osilodrostat?

Only partly. Both reduce cortisol production, but metyrapone has a distinct diagnostic role and a different clinical profile. Osilodrostat is positioned primarily as a newer chronic treatment for endogenous Cushing's syndrome.

References

1. HRA Pharma Rare Diseases. (2023). Metopirone 250 mg hard capsules: Summary of product characteristics.
2. Fleseriu, M., Auchus, R., Bancos, I., et al. (2021). Consensus on diagnosis and management of Cushing's disease: A guideline update. The Lancet Diabetes & Endocrinology, 9(12), 847-875.
3. U.S. Food and Drug Administration. (2023). Orange Book: Approved drug products with therapeutic equivalence evaluations.
4. European Medicines Agency. (2019). Guideline on the investigation of medicinal products for the treatment of Cushing's syndrome.